UFC 158 is full of welterweight fights, and one on the undercard has undergone a reshuffling. Canadian fighter Sean Pierson has been forced out of his bout with Rick Story, and has been replaced by former Strikeforce fighter Quinn Mulhern. Mike Johnston of Sportsnet explained the issues that kept Pierson off the card:

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@MikeyJ_MMA
Sean Pierson is out of UFC 158 after not being medically cleared. Pierson had been suffering effects from a concussion sustained at UFC 152.

Mulhern (18-2), a former King of the Cage welterweight champion, is currently on a three-fight winning streak. His only loss in Strikeforce came in his debut to Jason High. He'll meet Story (14-6), who is on a three-fight losing streak and desperately needs a win to keep his job in the UFC.

The bout will take place on the UFC 158 preliminary card. The March 16th card in Montreal will be headlined by a UFC welterweight title fight between champion Georges St. Pierre and former Strikeforce champ Nick Diaz.